Table pedestal

[fungus]

Hello,

I’m a user of Sketschup Free and I use it for some DIY projects at home. I’m not a Sketchup “expert”, so I need advice and help to avoid problems concerning a table pedestal project. Being aware of the knowledge and the helpful people at the Sketchup forum…

The project concerns the construction of a pedestal for a granite table.

I need to determent the exact measurements and the exact position of the parts and the best option to do this is Sketchup.

Hopefully it will be understandable what I mean by that with the explanation that follows and hopefully the explanation isn’t too extensive. Also apologies for my grammar as English is not my native language.

Keep in mind that the project is meanly a welding operation and to do that in a proper way and to achieve the right end result, I need a mold with the exact measurements .

The pedestal will be made of 34 RVS Ø10mm rods and 2 RVS Ø 12mm rods. The 2 RVS Ø 12mm rods will be transformed into 2 rings. One at the bottom and one at the top of the pedestal.

The centerline of the ring at the bottom on the drawing, has a Ø 599mm. The centerline of the ring at the top on the drawing has a Ø 479mm.

The distance between the centerlines of the 2 rings will be 666mm. The total height of the pedestal will be 666mm + (2x6mm) = 678mm.

The 34 rods will be weld between the 2 rings.

The end result is to become a form like sketch number 6. The goal is a “twisted” waist with the 34 rods almost closing the waist/ almost touching each other in the waist part. And here I need the knowledge of the forum to become the exact distance between the parts. More explanation on this…

The steps I made are going from sketch 1 to 6:

The fact that a circle in Sketchup is made from line identities is an advantage in this case and makes it easy to divide the circle in 34 sections.

The length of the line identities is also indicated in the Entity info. This length is the distance between the center lines of the 34 rods and is used to create the anchor points in the mold. I assume this length is correct ( anyway, I had a exact division of the circles form when I created the mold)

To achieve the waist form:

If the ascending rods between the 2 rings are connected from anchor point 1 ( on the red axis) below to anchor point 1 above and so on, a kind of cone form is created.

If the upper ring is rotated counter clockwise, the rods will follow and the waist will be formed.

In sketch number 2, I directly connected anchor point 1 from the bottom with anchor point 15 at the top.
A circle has 360°. With 34 sections you have 360/34= 10,5882° per section. So sketch number 2 has a rotation of 14x10.5882° = 148,2352°

Sketch number 5 has the same rotation but with the full body of the rods. If this would be the final choice the length of the rods indicated by the Entity Info would be 84,327mm minus (2x 6mm from the rings). I assume I may rely on that info and perception (?)

Notice that this length is changing for each chosen rotation !

In sketch number 6, I did an extra rotation of 5,4921° (which is ½ a section; ½ of a line identity of the circle). The total rotation becomes 152,5293° ( witch are 15.5 sections).

Here my questions:

I like to have the rods as close as possible in the waist. Although I also have to consider the act of welding and tolerance.

The circle I used with the follow me tool, is not perpendicular with the centerline of the rod ( sketch 5). Do I have a wrong end result of the full rod ? How can I draw a perpendicular circle on that line ?

How to measure or find the real and smallest distance between the rods in the waist?

Or, how to determine the magnitude of the rotation to achieve a distance of 1mm or 2mm at the waist. Or is this always a trail and error case ?

Again, because of the coherence between the rotation and the length of the rods and the construction of the mold, I need to know the exact measurements.
Notice I do not have to use the degrees of rotation; I can translate the magnitude of rotation in to the line identity’s and anchor points on the mole.

So dear experts, I need your knowledge and helpfulness and many thanks in advance for that.

GB
vortex table pedestal 2022.skp (613.8 KB)

[DaveR]

@fungus

How can I draw a perpendicular circle on that line ?

You can construct a face perpendicular to the edge using intferencing. Start with a perpendicular edge and then complete a face aligned with the long edge. Extrude the face with Push/Pull. Then end face will be perpendicular to the line. Erase the unneeded faces.

@fungus

How to measure or find the real and smallest distance between the rods in the waist?

I think I’d draw another circle at the height of the waist that is close to yur desired radius. Then look at the centrline of the rod as you try different points.

One thing I would suggest is that you use components to prevent geometry from sticking to other geometry. That would make this a whole lot easier to deal with.

@fungus

I need to know the exact measurements.

In Model Info you can increase the display precision to get more precise dimensions.

Any particular reason for 34 rods? 36 might be easier to deal with even though it means more pieces and welds in the shop.

[Wo3Dan]

All measurements seem to be drawn at scale, factor 10x

The top ring in your model is drawn with Ø 476mm, yet the text says it is Ø 479mm.

The bottom ring is correct, Ø 599mm.

So is the height, between rings, 666mm

[fungus]

DaveR & Wo3Dan, thanks for the reply.

@Wo3Dan;
Indeed, I’ve used a scale factor x 10 and forgot to mention it, sorry.
And indeed I also made a mistake with the radius of the top ring. The right radius has to be 23,95 ( x10) instead of 23,8 I’ve used. I’ll have to change it. Thanks for the attentiveness

@DaveR
Good suggestion to use components. Normally, I always use groups or components. In this case,
my goal was to stick the “rods” on the top ring and take them with the rotation to form the waist. Maybe a wrong idee from me and maybe there is a better way ?
The number of rods: the use of rotation degrees are helpful in the drawing and indeed with 36 rods and the correspondent 10° it would be easier in the drawings.
In the context of the mole construction, the rotation degrees are not so useful and even hard to use . The anchor points are the easiest way to determine the position of the rod on the top ring.
(An other point was the preferred distance between the rods on de rings).

The suggestion to draw another circle: a few points appear to me in this line of thinking.
A point of attention, concerning the height of the waist, is to find out if the height on the smallest point of the waist is permanent and not changing according to the angle of the rods…

Also: if one cut the rods standing in an angle, the cross section isn’t a circle but a ellipse that keeps changing when the angle is changing.

Exploring the height of the waist: (in this reasoning: the lines are the centerlines of the rods)
If I draw a line from anchor point 1 (on red axle line) on the bottom circle to anchor point 18 on the top circle, then I have the smallest waist. This line is cutting the vertical centerline of the whole construction in let’s say point A.
If I draw another line from 1 to 17 then the length of that line will decrease in comparison with the length of the first line.
The question here is: what’s happens with point A. Is it going down or is it permanent on the same height ?
To find out : Is there a way in Sketschup to stabilize point A on the first line ( keeping the distance between point 1 and A the same) and move the line in a way that the line is connect with point 17 ( or 14; 13… maybe better because of the bigger difference in distance)
If the end of the line in point 18 was B then B is not the connection point on 17; point B is higher.
What happened with point A ?
If I have a stabilized point A, then it is possible to measure the height of point A and find out if A is going down etc…
Above all this: is this reasoning of me correct ?